Chasm: The Rift is a 3D first-person shooter. As a Marine, the
player has been sent inside a power plant to investigate the loss of
power at the plant. They later discover that a group of monsters known
as the Timestrikers are using the power to create ruptures in time that
allow them to invade the Earth in three different time periods: present
day, ancient Egypt, and medieval times. Timestrikers that have invaded
the present day are also taking control of a nuclear plant in order to
detonate a nuke that will destroy nearly all life on Earth.
The
game starts in the present day, as the player goes inside the power
plant and nuclear plant, battling strange-looking security guards and
security systems that have gone haywire. They will then find the rifts
that the Timestrikers are using to invade other time periods, eventually
winding up at the Timestrikers' military base in the distant future.
I have included some official patches and add-ons in the "extras" folder
